The study, published in the Mayo Clinic Proceedings, found among 185 consecutive patients receiving transurethral microwave therapy -- at four medical centers -- 42 percent experienced systolic blood pressure surges of more than 30 mm Hg, while 5 percent had surges of more than 70 mm Hg.

About 70,000 transurethral microwave therapy procedures -- the placing a microwave device within the prostate that is heated to destroy excess tissue -- are performed each year, usually in an office setting and typically involving patients ages 50 to 85.

"This patient population is at high risk of cardiovascular disease," lead author Benjamin Larson, a medical student at Cleveland Clinic, said in a statement. "Anecdotal reports of adverse blood pressure events during and after transurethral microwave therapy, and our own experience, led us to look back at the records to identify potential problems among these patients whose blood pressure had been monitored."

The study authors said the findings should not necessarily deter use of the six U.S. Food and Drug Administration-approved devices for transurethral microwave therapy, but precautions -- such as taking blood pressure readings throughout the procedure -- should be taken.